## Prime numbers.

def is_prime(n)
  if n < 2 then return false end  
  for i in 2..n
    if n % i == 0 then return false end
  end
  return true
end

def get_all_primes(n)
  res = []
  for i in 0..n
    if is_prime(i)
		list_append(res, i)
	end
  end
  return res
end

primes = get_all_primes(20)
assert(primes == [2, 3, 5, 7, 11, 13, 17, 19])

print('primes =', primes)